The present invention relates to a process for the culture of aerobic microorganisms.
The industrial culture of microorganisms is producing more and more positive interest. Indeed, it makes it possible to obtain the microorganisms themselves, to produce the compounds secreted by the microorganisms such as for example, enzymes, pigments or toxins, to produce metabolites such as antibiotics, vitamins or amino acids, or to transform biochemically certain defined compounds as is the case, for example, during the industrial manufacture of citric acid.
Furthermore, the use of certain microorganisms as a source of proteins for animal or human food indicates a possible solution to the world food resources crisis.
Microorganisms have in fact the advantage over plant and animal organisms usually used for food in that they have a particularly high rate of growth. This much higher productivity ought to permit a considerable increase in the quantities of food available.
Various processes have already been perfected according to which microorganisms are fed by being provided with very varied substrates to form biomasses, and protein concentrates that can be used for food are then extracted from these biomasses.
The majority of the microorganisms used for this purpose are aerobic microorganisms. The culture plants must thus be fed with air or oxygen in order to ensure the growth of the microorganisms. However, as the solubility of oxygen in water is very low, the rate of growth of microorganisms is often limited by the rate of dissolution of oxygen in the water.
In order to overcome this disadvantage, it has been proposed in British Pat. No. 861,784 filed on Jan. 10, 1958 in the name of Armour and Co. to use an aqueous solution of hydrogen peroxide as a source of oxygen. The substrates used are substrates that are currently used for the culture of microorganisms, namely, products rich in carbohydrates (molasses, peptone, glucose, lactose) or proteins. These products however have great disadvantages which make them less interesting to use as substrates from an economic point of view. Indeed, these substrates are elaborate products, some of which could be suitable such as they are, without any modifications, for animal or human food. On the other hand, certain others of these products are agricultural by-products and because of this fact complex preliminary treatments are necessary before they can be used as substrates.
In another context, for economic reasons, people have turned towards the use of substrates made up of much simpler molecules such as those derived from protroleum products. It has thus been proposed in British Pat. No. 914,568, filed on Aug. 16, 1961 in the name of British Petroleum Company Limited to grow microorganisms in the presence of oxygen and hydrocarbons such as kerosene. The extension of this process to very light substrates such as methane, methanol and mixtures of hydrogen with carbon monoxide or carbon dioxide come up against great problems due to the inflammability of the mixtures of these products with oxygen.